This research project is concerned with the elucidation of the mechanism of physiologically important reactions. Two important objectives of this study are the detection of reaction intermediates and the delineation of elementary steps in complex biological processes. The particular types of biological systems under investigation include metabolic control through allosteric enzymes, organized enzymes, membrane-bound enzymes, and transport through membranes. Fast reaction techniques such as stopped-flow and temperature jump are utilized as well as more conventional equilibrium and kinetic methods. Fluorescence energy transfer and nuclear magnetic resonance measurements are used for structural mapping of macromolecular structures. A portion of this project is concerned with the improvement and development of physical methods which can be applied to biological systems. The specific systems under study include fatty acid synthase, a multienzyme complex; chloroplast coupling factor, an enzyme that synthesizes ATP and pumps protons across membranes; and an ATPase from yeast that also pumps protons across membranes. The long term goal of this work is to understand complex biological mechanisms in terms of molecular structure.